#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=63;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
LL a[maxn],b[maxn];
LL p[maxn];
int main(void)
{
  cin.tie(0);std::ios::sync_with_stdio(false);
  p[0]=1;
  for(LL i=1;i<=62;i++) p[i]=p[i-1]*2;
  LL l,r;cin>>l>>r;
  if(l==r){
    cout<<"0"<<"\n";
    return 0;
  }
  LL sum=0;
  for(LL i=62;i>=0;i--){
    if((r&p[i])!=(l&p[i])){
        for(LL j=i;j>=0;j--){
            sum+=p[j];
        }
        break;
    }
  }
  cout<<sum<<"\n";
return 0;
}
